Matched fuse for multicircuits



Sept. 2, 1947. ROGOFF 2,426,844

MATCHED FUSE FOR MULTICIRGUITS Filed Nov. 30, 1945 3.5 j@ J3 2305 QJ I 3g M Q4 25 Q@ 27 32 3] 22 14@ l 32 Patented Sept. 2, 1947 2,426,844 MATCHED FUSE Foa MULTICIRCUITS Julian Rogoff, New Rochelle, N. Y., assigner to Burndy Engineering Company, Inc., a corporation of New York Application November 30, 1943, Serial No. 512,405

(ci. o- 113) 2 Claims.

This invention relates to a fuse for multiwire circuits and more particularly to a matched fuse for use in a three phase system for aircraft.

.'The development of the three phase system for combat bombing planes has occurred concurrently with the need for parallel circuits to prevent disabling the entire electrical system with a single well placed shot. As a result the parallel circuit has been provided to produce continual maintenance of the electrical system through' alternate routes. The primary object of my invention is to provide a matched fuse for such a system.

When a fault occurs in a three phase system the fault currents will seldom be of the same magnitude in the three phases. The fusible element in the phase carrying the greatest fault current will blow or clear first and in this interval a fusible element in another phase may h'ave carried a fault current of suicient magnitude and for a sufficient length of time to alter or damage the fuse characteristics appreciably without destruction. In such cases the remaining fusible elements should be replaced even though apparently sound. If not replaced such a fusible element might not operate at rated capacity and possibly not coordinate with the remaining fusible elements in the circuit. Therefore it is desirable to have a three phase matched fuse with all three fusible elements locked together so that one cannot be replaced without replacing all three.

Another object therefore is to provide a fuse for a multi-phase circuit which provides fusible protection for all phases and which can be replaced only as a matched unit. A corollary object is to provide the matched unit in a unitary device which may be inserted and withdrawn as a single unit.

Moreover since space is at a premium in combat planes it is highly desirable to provide the matched fuse for the system in the smallest possible area and volume, and of minimum weight. Accordingly, a further object is to provide my fuse in a single assembly wherein some of the parts used for one of the fuse links may be made to serve its function with respect to the other fuse links, thus reducing the number of parts. V

Where under combat conditions it is found necessary to replace Vthe matched fuses, the time spent in removal and installation may mean the difference between life and death. An additional object therefore is to provide a matched unit that can be easily and quickly replaced, in a simple operation. A corollary `object is to provide means for quickly and visually identifying the blown fuse, so that the minimum time is lost in locating the incapacitated element.

VThe installation of a matched fuse for a three phase electrical system introduces additional problems of proper electrical connections. A still further object therefore is to provide means whereby a matched fuse may be installed in a multi-phase system, as expeditiously as possible, with' proper phase to phase connections through the fuse, and to do this as automatically as possible.

Still another object is to provide a matched fuse assembly which requires no additional support other than that carrying the cables, or conversely to provide means for supporting the cables tothe matched fuse base which has its own independent support, depending on the existing conditions. `In the latter case, there is provided a sturdier arrangement with a corresponding reduction in the vibration which may be aggravated by the wiresthemselves. I l

A properly protected electrical system requires a substantial number of fusible elements, and it is therefore desirable to produce such fuses as inexpensively as possible for the high cost alone maymilitate against the adoption of the protected system despite the many advantageous features.

I accomplishthese and other objects and obtain my new results as willbe apparent from the device describedrin the following specification, particularly pointed out in the claims, and illustrated in the accompanying drawing` in which:

Fig. lis a side elevation of my device, attached to a wall structure, with one ,separable end removed and shown in section through two of the fusible elements. y

Fig. 2 is an end view thereof. y

Fig. 3 is a top view of a modified structure.

Fig. 4 is a sectional side elevation.

Fig. 5 is a transverse sectional view of Fig. 4, taken along the line 5- 5 thereof.

In the drawing, Figs. A1 and 2, I have shown one form of matched fuse. This comprises a transparent cylindrical tube Il), containing two end plugsv Il, a Y-shaped separator l2, three fusible elements I3, two cap members I4, and two end sets of three separable connectors, each connectorcomprising two interlocking-halves l1 andY i8, VThe fusiblerelement I3, is positioned in each compartment I6 of the Y-shaped separator, which may bevmade of mica, and extends through the twoend plugs Il, where they are brazed to the connector halves Il. Recesses i9, 20 and 2|, may be provided in the end plugs, to permit the separator and fusible elements to be cemented to the end plug and the end plugs to be cemented to the inside of the glass tube. The two cap members have recesses 22 positioned on the inner sides thereof for supporting in position the enlarged ends 23 of the connector halves I1, when the cap members I4 are cemented in position on the ends of the transparent tubes Ill.

Each connector half has a pair of extending interlocking fingers 24 and 25, one of which carries a drop cam 26 approximately midway thereon for interlocking the two halves together under resilient pressure. The two halves will separate under the application of a predetermined longitudinally applied tensile force. These connectors are shown in greater detail in copending application Serial No. 473,414.

The connections are made by attaching the two connecting plugs, 21 made of insulating material each provided with three apertures 28 for carrying a set of connector halves IB, therein. These apertures are large enough to allow the extending fingers 24 and 25 to expand therein when the connection is made. The ends of connector halves I8 are similarly enlarged, as at 29, and iixedly positioned in recess 30. by the connecting plug cap member 3| which is cemented thereto. The cap member 3l is also apertured to allow the cable connection 32 to be made to the connector halves I8.

The connectors are properly aligned, in the modification shown by providing a centrally projecting member |40.. grooved as at |41), to enter the recessed slot 21a of the connecting plug 21 having a corresponding tongue member 21h. When the tongue is fitted to the groove, the connector halves are keyed to each other to establish proper phase connections.

In Fig. 1, the glass tube I with extending connector halves, I1 are supported by a pair of curved spring acting members 33 so that the tube may be quickly inserted or removed therefrom. The springs may be attached to an insulating section 34 through which connections 35, the familiar lock nut type being illustrated, may hold the insulating section and tube to a metal wall 36, the opposite side of which may similarly be provided with an insulating section 31.

The materials used in making the foregoing structure may be varied, it being desirable to make the tube transparent for visually determining the condition of the fusible elements, and sufliciently resistant to temperature and stresses to avoid breaking. The end plugs may be of cementitious material which is flame resistant, light in weight and capable of being sealed into position and supported without leakage or fracture.

The various compartments I6 containing the fusible elements may be sealed from each other, and provided with air or gas, at predetermined pressures, so that the operating characteristics of the fuse may be maintained at any outside pressure.

By the foregoing .construction I have shown a set of three fusible elements, which may be carefully matched, for connection to a three phase or multi-wired electrical System. In the event one of the fusible elements is clearedf the two connecting plugs 21, with their connections, may be quickly separated from the glass tube I0 and associated parts, and a new glass tube with extending connector halves quickly inserted and properly aligned therein.

The springs 33 and supporting structure need not be used if the cables 32 are capable of Withstanding the additional weight. In the form shown, independent Vibration is eliminated and this construction is probably more useful for airplane installation.

In Figs. 3, 4 and 5, I have illustrated a modified form of matched fuse, wherein the fusible elements may all be removed as a single unit by one motion of the hand.

Here the fusible elements 40 are contained in a plug like housing 4l, having a transparent top 42 and six extending terminal connections 43, all insertable in the socket base 44 to which the conductors 45 are connected by means of connections 46.

In the plan View of this modification shown in Fig. 3, the three,` fusible elements 40 are each positioned in compartments 41 formed by the wall structure 48 provided in the moulded housing 4l, between compartments. Transversely raised portions 49 extend midway across between walls forming a bridge between the two ends of the fusible elements, and prevent the fused ends from reestablishing the connection. Each end of the fusible element is connected to a pin-type connection 50, and cemented as at 5I, in position.

Thesocket base 44 comprises top and bottom members 52 and 53, held together by securing means 54. The pin connections 50 are inserted through corresponding apertures 55 and engage wiping contact ends 56, of the conductor sleeve 51, indented as at 58 to the conductors 45. Spring sleeves 59 maintain the contact ends 56 in resilient engagement with the pin connections 50. The socket base may be attached to a supporting surface GG, by the securing means 54.

By the foregoing constructions I have devised a fuse unit having a plurality of fusible elements individually and permanently mounted in a housing, which fuses may be atmospherically sealed to operate with predetermined characteristics, and all immediately replaceable as a single unit by a quickly detachable housing. Connections may be of the self aligning type to insure proper phase relationship. Connections may be of the pressure type with snap action contact or of the resilient pressure type, i. e. the pin type of socket connection.

I have thus described my invention, but I desire it understood that it is not confined to the particular forms or uses shown and described, the same being merely illustrative, and that the invention may be carried out in other ways without departing from the spirit of my invention. and, therefore, I claim broadly the right to em ploy all equivalent instrumentalities coming within the scope of the appended claims, and by means of which, objects of my invention are attained and new results accomplished, as itis obvious that the particular embodiments herein shown and described are only some of the many that can be employed to attain these objects and accomplish these results.

I claim:

1. A matched fuse unit for insertion into a multi-wire system comprising a plurality of fusible elements each insulated from the other; insulating means for supporting said fusible elements, said means permanently and non-removably mounted to each other to form a single unitary structure therefor; means for attaching electrical conductors to each end of the fusible elements, said fusible elements and supporting means constituting the single unitary structure,

5 attached to and removable from said electrical conductors only as a single unit.

2. The matched fuse unit of claim 1, wherein the plurality of fusible elements are collectively provided with a single transparent cover mounted to the supporting structure.

JULIAN ROGO'FF.

REFERENCES CITED The following references are of record in the le of this patent:

Number UNTTED STATES PATENTS Name Date Mason July '7, 1931 Magee Apr. 18, 1933 Sprague Apr. 1, 1902 Hatzel et a1 June 25, 1907 Pond June 18, 1940 Murray Apr. 16, 1912 Briggs May 15, 1923 Harvey Feb. 6, 1934 

